Spence Shale

SPENCE SHALE Member - Langston Formation
Upper Middle Cambrian 510 ~ 504 Mda
Carlo Kier Collection

In these pages are illustraded the trilobites collected or acquired from the SPence Shale member by my friend Carlo Kier.
The fossils are organized by Order of appartenance. Click on the order distribution poster to show it at full resolution or click to this address to access to the poster with the nine orders of trilobites (I’m working for the version 2). All these marvellous trilobites are wonderfully prepped by Dave Comfort. The list it is not clearly exaustive and will be upgraded periodically.

The Spence Shale was named by Walcott (1880) as a member of the Ute Formation and described as argillaceous shales, and he later added the words of sandy shales.
It was named in honor of Robert S. Spence of Garden City, Utah, who in 1896 and subsequent years sent some interesting and well-preserved fossils to Dr. Charles D. Walcott at the U.S. National Museum. His doing so led to Dr. Walcott's studies and collections at Spence's discovery site and other localities in southern Idaho and northern Utah.
Williams and Maxey (1941) later recognized that the Spence Shale was a member of the Langston Formation, separated from the Brigham Quartzite by only a few feet of crystaline limestone.
More recent authors have used the name Spence to refer to the Spence Tongue of the Lead Bell Shale, the preferred usage today.

Viaggio a trilobiti nelle Spense Shale con Jake, Tomas e Luc 012

The lower part of the Spence, containing agnostid trilobites, consists of dark silty micrite and gray to gray black laminated shales considered to represent outer detrital-belt environments. The upper part of the Spence lacks agnostids and has some thin-bedded limestone.
Below the Spence Shale is the Naomi Peak Limestone, which represents the middle carbonate bank, and the massive Brigham Quartzite below it represents the inner detrital belt.
Spence Shale of variable thickness crops out at several localities in the Wasatch Mountains north of Brigham City and in its eastern spur, the Bear River Range, extending into southern Idaho.

At left are showed the typical gray shales of the Spence Shale member

Useful links:

http://geology.utah.gov/surveynotes/gladasked/trilobites.htm
http://www.geo-tools.com/trilobites.htm
http://www.geo-tools.com/007-03.htm
http://www.westernta.com/Formations/Spence.htm
http://www.earth.utah.edu/utahfossil/SpenceShaleWM.html
http://www.utahgeology.com/stratcolumns.php?URLVariable=strat_16
http://paleodb.org/cgi-bin/bridge.pl?action=displayStrata&group_hint=&group_formation_member=Langston
http://paleodb.org/cgi-bin/bridge.pl?action=displayCollResults&formation=Langston&member=Spence%20Shale

Source for trilobite description:
Treatise of Invertebrate Paleontology, Part O, Arthropoda I, Raymond Moore (Directed by), 1959
P.A.Jell and J.M.Adrain.(2002) - Available generic names for Trilobites, Mem. of the Queensland Museum 48(2): 331-553

Click on name to access directly to the trilobite:

Amecephalus idahoense	Spencia typicalis
Amecephalus laticaudum	Syspacephalus spencei
Athabaskia bithus	Zacanthoides idahoensis
Chancia ebdome	Zacanthoides typicalis
Glossopleura packy	Undescribed
Glossopleura bion
Kootenia spencei	Gogia sp.

Order: PTYCHOPARIIDA

Large, heterogenous order with primitive origins and problematic classification, with specialized offshoots that are hard to frame within a general diagnosis.

Cephalon typically with opisthoparian facial sutures, with gently forward-tapering simple glabella bearing a broad, rounded front, usually with 3 pairs of rather narrow parallel glabellar furrows; natant hypostome. Thorax typically large with 8+ thoracic segments. Pygidium quite variable, but typically with a small pygidium bearing a border (Cambrian) or a larger pygidium with or without border (post-Cambrian).
From: http://www.trilobites.info/ordptychopariida.htm

Amecephalus idahoense, Resser, 1939

Ord.: PTYCHOPARIIDA
Fam.: ALOKISTOCARIDAE
Gen.: Amecephalus, WALCOTT, 1924b

Border of cranidium wide and flat except for low boss in front of glabella and shallow border furrow; glabella defined by strong axial furrow, eyes ridge crossing fixigenae and librigenae spined. Thorax with about 19 segments; pygidium small.

Amecephalus laticaudum, Resser, 1939

Ord.: PTYCHOPARIIDA
Fam.: ALOKISTOCARIDAE
Gen.: Amecephalus, WALCOTT, 1924b

Border of cranidium very wide and flat except for low boss in front of glabella and shallow border furrow; glabella defined by strong axial furrow, eyes ridge crossing fixigenae and librigenae well developed. Thorax with about 19 segments; pygidium small (see the upper right image).

Chancia ebdome, Walcott, 1924

Ord.: PTYCHOPARIIDA
Fam.: ALOKISTOCARIDAE
Gen.: Chancia, WALCOTT, 1924

Frontal area shorter and less bowed forward that in Alokistocare, glabella defined by axial furrows, eye ridges crossing fixigenae, librigenae spined; thorax with 19 to 22 segments, pleurae with well defined furrows. pygidium small.

Spencia typicalis, Resser, 1939a

Ord.: PTYCHOPARIIDA
Fam.: PTYCHOPARIIDAE
Gen.: Spencia, RESSER, 1939a

Strongly convex, anteriorly rounded glabella with lateral furrows; eye ridges distinct; palpebral lobes short, librigenae with poorly developed genal spines. Thorax with rounded extremities and little pygidium.

A specimen of Gogia sp. is visible on the right side of the picture.

Syspacephalus spencei (?), Resser, 1939a

Ord.: PTYCHOPARIIDA
Fam.: PTYCHOPERIIDAE
Gen.: Syspacephalus, RESSER, 1936

Glabella low, sloping down anteriorly; anterior border furrow more or less obsolete medially; palpebral lobes anterior to glabellar mid-point; anterior facial sutures convergent; genal angle rounded. Thorax of 13 to 15 segments. Exoskeleton slightly flattened. Pygidium small.

Order: CORYNEXOCHIDA

Cephalon with opisthoparian sutures; glabella elongate, sides often concave (pestle-shaped), furrows (when not effaced) typically with splayed arrangement, the hind pair pointing sharply backwards, and anterior pairs tending more and more forward directed; sometimes furrows pit-like; cranidial borders often ledgelike; hypostome conterminant or (in derived forms) impendent; eyes typically large, in some gently arcuate.
Thorax typically with 7-8 segments (but range for order is 2-12, rarely more), pleural tips often spinose.
Pygidium typically large (isopygous or subisopygous), of variable form, sometimes spinose.
From: http://www.trilobites.info/ordcorynexochida.htm

Athabaskia bithus, Walcott, 1916

Ord.: CORYNEXOCHIDA
Fam.: DOLICHOMETOPIDAE
Gen.: Athabaskia, RAYMOND, 1928

Glossopleura packy,

Ord.: CORYNEXOCHIDA
Fam.: DOLICHOMETOPIDAE
Gen.: Glossopleura, POULSEN, 1927

Long palpebral lobe, slightly tapering posterior area of fixigenae. Cranidium without anterior border; axial furrows effaced between anterior corners of glabella; genal angles produced into into fairly strong, backward-directed genal spines. Thorax with 7 segments, wide axis and pointed extremities. Pygidium sligthly smaller than cephalon with indistinctly segmented pleural fields and well defined wide, concave border. Spines are presents in this specimen starting from 5th, 6th and 7th axial segments.

Zacanthoides idahoensis, Walcott, 1908

Ord.: CORYNEXOCHIDA
Fam.: ZACANTHOIDIDAE
Gen.: Zacanthoides, WALCOTT, 1888

Glabella parallel-sided; metafixigenal spides present. Long semicircular palpebral lobesThorax of 9 segments; pleurae obliquely furrowed; no macropleural segments. Axial macro-spine on last axial segment. Pygidium smaller than cephalon with elevated, abruptly terminated axis; general outline subtriangular; pleural fields flat; marginal furrow and border indistinct; pleurae directed backward, extended intoseveral pairs of marginal spines

Zacanthoides typicalis, Walcott, 1886

Ord.: CORYNEXOCHIDA
Fam.: ZACANTHOIDIDAE
Gen.: Zacanthoides, WALCOTT, 1888


	Kootenia spencei, Resser, 1939 Ord.: CORYNEXOCHIDA Fam.: DORYPYGIDAE Gen.: Kootenia, WALCOTT, 1889

Glossopleura Bion, Spense Shale, Cambrian UT (1)

Glossopleura bion, Walcott, 1916

Ord.: CORYNEXOCHIDA
Fam.: DOLICHOMETOPIDAE
Gen.: Glossopleura, POULSEN, 1927

Order: UNDESCRIBED

Order: CRINOZOA (Phylum ECHINODERMATA)

Phylum: Echinodermata
Class: Crinoidea
Order: Crinozoa
Family: Eocrinoidea
Genus: Gogia

Species: Gogia spiralis ? (probably new species)

Gogia was one of the first, if not the first known, genus of the early echinoderm class, Eocrinoidea, from the Cambrian. The species of Gogia, like other eocrinoids, were not closely related to the true crinoids, instead, being more closely related to the blastoids.
Gogia is distinguished from sea lilies, and most other blastoids, in that the plate-covered body was shaped like a vase, or a bowling pin (with the pin part stuck into the substrate), and that the five arms were split into pairs of coiled, ribbon-like strands.
As a whole, the Eocrinoids were believed to be ancestral to Blastoidea.
(Source: http://en.wikipedia.org/wiki/Gogia )


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